Method of and a device for automatically milking a dairy animal

ABSTRACT

A method of automatically milking a dairy animal, in particular a cow. The method comprises: a) the step of activating the teat cup for milking the teat; b) the step of measuring a milking parameter during milking the teat during step a) for obtaining a value of the milking parameter, and c) the step of deactivating the teat cup when a deactivation threshold has been reached. The deactivation threshold is determined at least partially with the aid of the value of the milking parameter. A device for automatically milking a dairy animal, in particular a cow. Said device is provided with means for activating the teat cup for milking a teat of the dairy animal, means comprising a milking parameter for measuring a milking parameter during milking the teat for obtaining a value of the milking parameter, means for deactivating the teat cup, and means for generating a threshold signal indicating that a deactivation threshold has been reached. The deactivation means are put into operation with the aid of the threshold signal, the means for generating the signal indicating a deactivation threshold generating the signal at least partially with the aid of the value of the milking parameter.

[0001] The invention relates to a method of automatically milking a dairy animal, in particular a cow, according to the preamble of claim 1.

[0002] The invention further relates to a device for automatically milking a dairy animal, in particular a cow, according to the preamble of claim 37.

[0003] Such a method and device are known from the internal application WO 00/18218. Although in this application numerous possibilities are described with respect to the moment when milking by means of a teat cup is stopped, at the present moment there appears still to be a need for a method and a device by means of which it is possible to determine per dairy animal individually the moment when milking can be stopped, so that a dairy animal can optimally be milked with respect to i.a. udder health and the like.

[0004] It is an object of the invention to supply this need.

[0005] For that purpose, according to a first aspect of the invention, a method of the above-described type comprises the measures of the characterizing part of claim 1. Due to the fact that the deactivation threshold is determined at least partially with the aid of the value of the milking parameter, the deactivation threshold can be adapted to the present momentary situation and the values of the milking parameter measured at that moment can be taken into account. This provides a considerable improvement relative to the existing pre-set deactivation thresholds.

[0006] For the milking parameter there is preferably selected one milking parameter from the group consisting of milk flow, milk yield, milk temperature, electric conductivity of the milk, fat content of the milk, protein content of the milk, cell count of the milk, intervals between milk gushes, duration of the milk gushes, and the peak and off-peak values of the mentioned milking parameters. Although other parameters may also be applied, these parameters have appeared to be the most efficient ones for determining the deactivation threshold.

[0007] It is particularly advantageous when for the value of the milking parameter an average value is chosen. Due to this, fluctuations or temporary perturbations present by nature in the measured values are averaged, and a more accurate determination of the deactivation threshold becomes possible.

[0008] In an embodiment of a method according to the invention the method comprises the step of recording in step a) a starting time from which the average value of the milking parameter is determined. As a starting time from which the average value of the milking parameter is preferably determined the starting point of time when the milk flow in step a) starts. In some cases the selected milking parameter shows strongly fluctuating values at the beginning of the start of the milk flow, so that it is advantageous to determine, as a starting time from which the average value of the milking parameter is determined, a point of time after the starting time when the milk flow in step a) starts. Such a period of time may vary; in dependence of the milking parameter, between some seconds and some tens of seconds.

[0009] The average value of the milking parameter is preferably recorded continuously from the starting time. Although continuously recording the average value requires considerable calculation capacity, this results in extremely accurate values.

[0010] In an embodiment of a method according to the invention the method comprises the step of determining and storing the momentary value of the milking parameter. Here by storing is meant keeping the value of the milking parameter at least as long as is necessary for processing the value.

[0011] Although the value of the milking parameter may be used as such to deactivate the teat cup, it is preferred when a mathematical function is applied to the value of the milking parameter for obtaining a threshold milking parameter value. By choosing the function in dependence of the wishes, a manager or farmer can adapt the deactivation of the teat cup according to his own views.

[0012] In an advantageous embodiment of a method according to the invention the method comprises the step of comparing the momentary value of the milking parameter with the threshold milking parameter value, the step of deactivating the teat cup preferably being carried out when the momentary value of the milking parameter equals or is lower than the threshold milking parameter value. For being insensitive to usually occurring fluctuations or perturbations, the step of deactivating the teat cup is preferably carried out when the momentary value of the milking parameter equals or is lower than the threshold milking parameter value during a period of time. The period of time is preferably adjustable, in particular between approximately 2 seconds and approximately 9 seconds.

[0013] It has appeared that ending of the milking can be carried out without unfavourably influencing the udder health, in that the method comprises the step of storing in a memory of a computer a number of ranges of average milking parameter values, and of storing in a memory of the computer a respective threshold milking parameter value corresponding with a certain range. For example, with cows, at the following average milk flows, i.e. more than 500 ml/min.; between 370 and 500 ml/min.; between 250 and 370 ml/min.; between 170 and 250 ml/min., and less than 170 ml/min., the following threshold milk flows respectively appear to give good results: 400 ml/min.; 120 ml/min.; 50 ml/min.; 30 ml/min., and 20 ml/min.

[0014] When comparing the average milking parameter value with the ranges stored in the memory demonstrates that the momentary value of the milking parameter value equals or is lower than the threshold milking parameter value corresponding with the average milking parameter value, deactivation of the teat cup can take place.

[0015] In an embodiment of a method according to the invention, in which the method comprises the step that, when the average of the threshold milking parameter value equals or is lower than the threshold milking parameter value, deactivation of the teat cup takes place when the momentary value of the milking parameter equals or is lower than the threshold milking parameter, a deactivation of the teat cup takes place each time when the threshold milking parameter has been reached. This prevents the teat from being milked too long.

[0016] From long research it has been found that a quick deactivation of the teat cup, for example when it is expected that many dairy animals have to be milked within a short period of time, is carried out correctly when the function consists in dividing the value by 3. A non-quick deactivation takes places in particular when the function consists in dividing the value by 5. It will be obvious that the indicated values are guide values, from which may be deviated within the limits of experience.

[0017] The method preferably comprises the step of determining, during obtaining a milk flow, the values of several milking parameters, the deactivation threshold being determined at least partially with the aid of the values of at least two measured milking parameters. Thus it is possible to take into account several values obtained during milking for deactivating the teat cup.

[0018] Although by means of the inventive method a deactivation threshold is determined during milking, in some cases it may be advantageous that the method comprises the step of determining, during obtaining a milk flow, the value of at least one milking parameter, and that the deactivation threshold is determined at least partially with the aid of the value of the at least one measured milking parameter and a predetermined milking parameter value which is in particular based on historical data. Accordingly, there is already a deactivation threshold from the beginning of the milking, said deactivation threshold being adapted during milking, according to the invention, with the aid of values of the milking parameters. It is noticed that the deactivation threshold obtained after the milking has ended may be used as a predetermined threshold for the next milking run.

[0019] In an embodiment of a method according to the invention the method comprises the step of determining the difference between the momentary value of the milking parameter and the predetermined milking parameter value which is in particular based on historical data. Such a deviation may also be used for determining the deactivation threshold.

[0020] It has appeared to be in particular practical when during step a) the value of the momentary milk flow, the value of the average of the milk flow and the value of the momentary electric conductivity of the milk obtained are determined. When the method additionally comprises the step of storing the average, historical electric conductivity of the milk produced by the teat based on historical data, by determining the difference between the momentary electric conductivity and the average, historical electric conductivity, there may be obtained a deactivation threshold which is advantageous with respect to udder health.

[0021] Alternatively or additionally an advantageous method according to the invention comprises the step of connecting at least one further teat cup to a further teat of the dairy animal, and the step of determining the electric conductivity of the milk obtained from said further teat.

[0022] When the method comprises the step of determining the teat which in comparison with the other teats produces at one point of time milk with the lowest electric conductivity, and of determining for every other teat the deviation from the conductivity of the milk produced by that other teat relative to the milk obtained from the teat producing the milk with the lowest conductivity, the step of deactivating the teat cup may be carried out at a point of time depending on the average milk flow and the difference in electric conductivity. As known, the electric conductivity may be used as an indication of possible mastitis, and the ending of the milking may be adapted thereto in this case by taking this electric conductivity into account. At an increased electric conductivity the point of time when the teat cup is deactivated is preferably postponed.

[0023] When the measured deviation is greater than a predetermined value, it is preferred when not the exact average milk flow, but a compensated average milk flow is taken as a starting time for deactivating the teat cup. This compensated average milk flow is in particular obtained in an advantageous manner when the method comprises the step of applying a mathematical function to the value of the average milk flow and the difference in electric conductivity for obtaining a compensated threshold milk flow average.

[0024] After long research it has appeared to be advantageous that, when the deviation is greater than 10%, a function consisting in multiplying the average milk flow by 10 and in dividing it by the difference in electric conductivity ensures that deactivation of the teat cup takes place at a point of time which is appropriate with respect to udder health.

[0025] Although disconnection of the teat cup may take place simultaneously with deactivation of the teat cup, it is preferred when the step of disconnecting the teat cup is carried out after a predetermined period of time has elapsed after deactivation of the teat cup. Said period of time is in particular adjustable. The period of time is preferably adjustable between approximately 2 seconds and approximately 15 seconds.

[0026] Although the inventive method is applicable in a conventional, automatic method of milking, the method is in particular advantageous when the automatic milking is carried out by a milking robot. In particular advantageous is an embodiment of a method according to the invention in which the admission criterion for the milking robot is at least partially adapted with the aid of the value of the milking parameter measured during step a), and/or the measured deviation. Just because the measured value indicates the momentary situation, it may be used for adapting the admission criterion. When the measured value indicates e.g. that the dairy animal is ill, the admission criterion may be altered in such a manner that the sick animal is not admitted. Moreover the measured value may indicate that the dairy animal develops or changes, so that an adaptation of the admission criterion is desired. Such an adaptation of criterion on the basis of the measured value may be carried out by a person skilled in the art without further data being required.

[0027] The invention further relates to a device for performing the above-described method. The invention particularly relates to a device of the above-described type comprising the measures of the characterizing part of claim 37.

[0028] Advantageous embodiments of the device according to the invention are described in the subclaims.

[0029] The invention will be elucidated hereinafter with reference to an embodiment shown in the drawing, in which:

[0030]FIG. 1 is a schematic arrangement of a device according to the invention, provided with one teat cup, and

[0031]FIG. 2 is a schematic arrangement of a device according to the invention, provided with four teat cups.

[0032] The invention will be described with reference to the first embodiment of a device 1 for automatically milking 10 a dairy animal, such as a cow, provided with one teat cup 2, shown in FIG. 1. The measures of the inventive method will be set out clearly in the description with respect to the device. Moreover, the invention will be explained in further detail by way of example with reference to a limited number of specifically mentioned milking parameters. However, it will be obvious that also other milking parameters than those described in the claims, may be used. For a person skilled in the art it is obvious that merely by experimental research the variation of the milking parameter can be measured during milking. Said deviation may then be used, possibly processed by a mathematical formula, for determining at least partially the deactivation threshold.

[0033] The teat cup 2 shown in FIG. 1 may be automatically connected and disconnected to respectively from a teat of a cow by means of a milking robot which is not shown in the figures. The milk yielded per udder quarter by means of the teat cup 2 may be supplied via separate milk lines 4 to a milk quantity meter or milk glass 3. The discharge line 5 of the milk glass 3 is coupled to a line 7 extending towards the milk tank 6. As known, the device 1 further comprises a pulsator system 8 for the teat cup 2. The vacuum line 9 for the pulsator system 8 is connected in a usual manner to a vacuum pump with balance tank.

[0034] In an obliquely downwardly extending portion of the milk line 4 there is included a milk flow meter 10 for establishing the start of the milk flow and for determining the value of the milk flow during milking, in other words during the time when the teat cup is active. Said milk flow meter 10 operates in this example on the basis of the creation by a milk flow of an electric connection between two electrodes. The tilted position of the milk flow meter 10 prevents milk from remaining between the electrodes, in other words prevents a small quantity of milk from being present between the electrodes; this would of course result in a milk flow being permanently observed. In the region of the milk flow meter 10 the milk line 4 has preferably such a diameter that irrespective of the milk flow present therein, the milk line is always completely filled.

[0035] In the milk line 4 there is also included a temperature meter 11 for establishing the milk temperature. The milk temperature is a good measure for the body temperature; with sick cows, such as cows affected by mastitis, the body temperature is higher than normally.

[0036] In the milk glass 3 there is disposed a conductivity meter 12 for determining the electric conductivity, e.g. for establishing mastitis or another infectious illness. Said conductivity meter 12 comprises a reservoir with electrodes for measuring the electric conductivity of the milk present in the reservoir. At each new milk flow the milk present in the reservoir is replaced. When the milk is affected, then an increased electric conductivity is established. Since for each new milk flow there is observed in the beginning a small increase of the electric conductivity, it is also possible to establish the start of a milk flow by using this mastitis sensor instead of the milk flow meter 10 or in addition thereto.

[0037] The outgoing signals S1, S2 and S3 of the respective meters 10, 11 and 12 are supplied to a computer 13 in which the information from these meters will be further processed, as will be elucidated hereinafter, and possibly be made visible on a display screen 14.

[0038] Between the line 5 and the line 7 there is further included a three-way valve 15 for discharging the milk flow from a quarter affected by mastitis of the udder of the cow to a waste tank 16. When, on the basis of the information communicated by the computer 13 the farmer decides to discharge milk to the waste tank 16 and gives for that purpose an appropriate command to the computer 13, the three-way valve 15 is switched over by means of a signal S4 supplied by the computer 13. The computer 13 may possibly transmit this signal S4 automatically to the three-way valve 15.

[0039] According to the invention the computer 13 may determine on the basis of the data from the milk flow meter 10 the starting time when the milk flow begins and preferably store said starting time (temporarily or permanently). Also the momentary milk flow as measured by the milk flow meter 10 may be stored by the computer 13. From these data the computer 13 continuously determines the average milk flow. Determination of the average milk flow may begin at the moment when the milk flow starts or, for not taking into account the first measurements which may usually contain noise or deviating values, when a predetermined period of time after the start of the milk flow, e.g. a period of time from 10 to 50 seconds, has elapsed. It is noticed that by storage is meant that the computer keeps the data, at least as long as necessary for processing them. For storing the data the computer 13 comprises one or more memories 17 (in the embodiment shown only one memory is depicted for the sake of simplicity).

[0040] The computer 13 comprises a processing member 18 suitable for applying a mathematical function to the value of the average milk flow. As a result of the mathematical function a threshold milk flow average is obtained. In dependence of the wishes a suitable function may be chosen. However, from long research it has been found that for a quick deactivation of the teat cup the function of dividing by 3 is highly appropriate irrespective of the individual cow. It further appears that for a non-quick deactivation the function of dividing by 5 is highly appropriate irrespective of the individual cow.

[0041] The computer 13 further comprises a comparator 19 for comparing the momentary milk flow with the calculated threshold milk flow average. When the comparison indicates that the momentary milk flow equals or is lower than the calculated threshold milk flow average (functioning as a deactivation threshold), the computer 13 supplies a signal S5 controlling the deactivation of the teat cup 2. For example due to the fact that the signal S5 controls the pulsation system 8 in such a manner that the vacuum is removed from the teat cup 2.

[0042] From long research it has also been found that it is possible to divide the average milk flow produced by cows into certain milk flow ranges, and to allocate a certain threshold milk flow to each of those milk flow ranges. Such milk flow ranges and corresponding threshold milk flows are stored in the memory 17 of the computer 13. An example of such ranges is represented hereinafter in table I. TABLE I Average milk flow range (ml/min) Threshold milk flow (ml/min) >500 400 370-500 120 250-370 50 170-250 30 <170 20

[0043] The comparator 19 of the computer 13 compares the measured average milk flow with the ranges stored in the memory, and the computer 13 determines the corresponding threshold milk flow. When the momentary milk flow equals or is lower than the threshold milk flow, the computer supplies the signal S5 for deactivation of the teat cup 2.

[0044] It is noticed that as a threshold milk flow also other predetermined threshold values may be taken, e.g. those based on historical data.

[0045] The signals issued by the meters 11, 12 during milking may be averaged over a certain period of time, e.g. over 24 hours, and/or over a number of milking runs. As the cow will be milked several times per day, this average value may each time be calculated as a progressive average. The conductivity meter 12 thus determines the momentary electric conductivity of the milk obtained and the computer 13 ensures the storage of the average, historical electric conductivity of the teat based on historical data.

[0046] This average, historical electric conductivity gives an indication about this parameter for that teat of that particular cow. When the comparator 19 of the computer 13 compares the momentary electric conductivity with the average, historical electric conductivity which is stored in the memory 17 of the computer 13, the difference between these values can be determined by the computer 13. Of course, there may be used an animal identification system known per se which for the sake of simplicity will not be detailed further.

[0047] When the difference exceeds a certain, to be pre-set value, the relevant teat may be infected, and the computer 13 may issue relevant signals for taking the necessary measures. In particular it is of importance for the health of the relevant cow that the teat is milked in another manner than when a normal conductivity value is detected. For that purpose the means, in the present case the pulsation system 8, for deactivating the teat cup 2 is put into operation by the computer 13 at a point of time depending on the measured average milk flow and the difference in electric conductivity. In particular the computer 13 applies a mathematical function both to the value of the average milk flow and to the difference in electric conductivity for obtaining a so-called compensated threshold milk flow average. It is then preferred that the function is such that at a raised conductivity the deactivation takes place at an other point of time than usually, in other words at an increased conductivity the teat will be milked longer.

[0048] After long research it has appeared to be advantageous that, when the deviation is greater than 10%, a function consisting in multiplying the average milk flow by 10 and in dividing it by the difference in electric conductivity ensures that the deactivation of the teat cup takes place at a point of time which is appropriate with respect to udder health.

[0049] It goes without saying that the average milk flow may also be used in combination with other milking parameters for putting the means for deactivating the teat cup into operation. When for example during milking the temperature meter 11 issues a value which clearly deviates from the relevant average value, i.e. is outside a certain tolerance range around the average value, this may be an indication of illness of the cow. The computer 13 may then be programmed such that in this case it is immediately decided to deactivate the teat cup 2 and to disconnect it from the teat. Moreover, the computer 13 may give a warning signal to the farmer.

[0050] In the embodiment shown in FIG. 2 the device 1 comprises four teat cups 2. Each of the teat cups 2 can be connected to a teat of a cow. Of the milk produced by each of the teat cups 2 the milk flow is determined by the milk flow meter 11, the temperature by the temperature meter 11, and the electric conductivity by the conductivity meter 12. These data are used according to the embodiment described with reference to FIG. 1.

[0051] However, in the embodiment of FIG. 2 the computer 13 determines the teat (teat cup 2) from which at one point of time the milk has the lowest electric conductivity. For every other teat (teat cup 2) the computer 13 determines the deviation from the electric conductivity of the milk produced by that other teat relative to the lowest conductivity of the milk obtained from the teat producing the milk with the lowest conductivity. In a manner analogous to that of the above-described embodiment the difference in the conductivity of the milk between the teats (teat cups 2) may be an indication of an infection in at least one of the teats. Like in the embodiment of FIG. 1 it is then advantageous that the means for deactivating the teat cup are put into operation by the computer at a point of time depending on the average milk flow and the difference in electric conductivity. It has appeared that as a function, the same function, i.e. multiplying the average milk flow by 10 and dividing it by the difference in electric conductivity, can be used advantageously.

[0052] Besides the means for deactivating the teat cup, the device 1 may comprise a (non-shown) milking robot known per se, said milking robot comprising means for automatically connecting respectively disconnecting the teat cup(s). These means may be identical to or integrated into the means for deactivating the teat cups. However, the computer is preferably suitable for determining a period of time from deactivation of the teat cup and for putting the means for disconnecting the teat cup(s) into operation when the period of time has reached a certain time threshold value. The time threshold value is preferably adjustable, a range between approximately 2 seconds and approximately 15 seconds having appeared to be advantageous.

[0053] It will be obvious that in some cases it is advantageous not to deactivate the teat cup immediately when the momentary value of the milking parameter equals or is lower than the threshold milking parameter value, but only when this situation occurs during a period of time, said period of time being adjustable e.g. between approximately 2 seconds and approximately 9 seconds. In particular the period of time amounts to 3 seconds.

[0054] Likewise average values may be determined from further signals which may be deduced from combinations of signals issued by several sensors. Likewise, in particular by the milk flow meter in combination with the quantity of milk per milking run collected in the milk glass 3, signals may be deduced being a measure for the milk velocity and/or the milk yield. Also the value of these signals may be averaged. The mentioned averaging processes are carried out in the computer 13 and will all relate to a particular animal or a particular group of animals and/or a particular period of time. The signals issued by one or more sensors during milking of separate animals and having a value deviating from this average value, may always be an indication that something is wrong with the health of the relevant teats. Such an indication may be given by the computer 13 on an attention list, i.e. both be made visible on the display screen 14 of the computer 13 and be printed. Besides there may be given an alarm, e.g. in the form of control lights to be disposed on the equipment or via the mobile telephone of the farmer. 

1. A method of automatically milking a dairy animal, in particular a cow, said method comprising: a) the step of activating the teat cup for milking a teat of the dairy animal, b) the step of measuring a milking parameter during milking the teat during step a) for obtaining a value of the milking parameter, and c) the step of deactivating the teat cup when a deactivation threshold has been reached, characterized in that the deactivation threshold is determined at least partially with the aid of the value of the milking parameter.
 2. A method as claimed in claim 1, characterized in that for the milking parameter there is selected at least one milking parameter from the group consisting of milk flow, milk yield, milk temperature, electric conductivity of the milk, fat content of the milk, protein content of the milk, cell count of the milk, intervals between milk gushes, duration of the milk gushes, and the peak and off-peak values of the mentioned milking parameters.
 3. A method as claimed in claim 1 or 2, characterized in that the value of the milking parameter is an average value.
 4. A method as claimed in claim 3, characterized in that the method comprises the step of recording in step a) a starting time from which the average value of the milking parameter is determined.
 5. A method as claimed in claim 4, characterized in that that as a starting time from which the average value of the milking parameter is determined the point of time is taken when the milk flow in step a) starts.
 6. A method as claimed in claim 4, characterized in that as a starting time from which the average value of the milking parameter is determined there is taken a point of time after the point of time when the milk flow in step a) starts.
 7. A method as claimed in claims 3 through 6, characterized in that from the starting time the average value of the milking parameter is recorded continuously.
 8. A method as claimed in any one of the preceding claims, characterized in that the method comprises the step of determining and storing the momentary value of the milking parameter.
 9. A method as claimed in any one of the preceding claims, characterized in that a mathematical function is applied to the value of the milking parameter for obtaining a threshold milking parameter value.
 10. A method as claimed in claim 9, characterized in that the method comprises the step of comparing the momentary value of the milking parameter with the threshold milking parameter value.
 11. A method as claimed in claim 10, characterized in that the step of deactivating the teat cup is carried out when the momentary value of the milking parameter equals or is lower than the threshold milking parameter value.
 12. A method as claimed in any one of the preceding claims, characterized in that the method comprises the step of storing in a memory of a computer a number of ranges of average milking parameter values, and of storing in a memory of the computer a respective threshold milking parameter value corresponding with a certain range.
 13. A method as claimed in claim 12, characterized in that the method comprises the step of comparing the momentary and/or average milking parameter value with the ranges stored in the memory.
 14. A method as claimed in claim 12 or 13, characterized in that the method comprises the step of deactivating the teat cup when the momentary value of the milking parameter value equals or is lower than the threshold milking parameter value corresponding with the average milking parameter value.
 15. A method as claimed in claims 11 and 14, characterized in that, when the average of the threshold milking parameter value equals or is lower than the threshold milking parameter value, deactivation of the teat cup takes place when the momentary value of the milking parameter equals or is lower than the threshold milk flow.
 16. A method as claimed in claim 9, characterized in that the function consists in dividing the milking parameter value by
 3. 17. A method as claimed in claim 9, characterized in that the function consists in dividing the milking parameter value by
 5. 18. A method as claimed in any one of the preceding claims, characterized in that the method comprises the step of determining, during obtaining a milk flow, the values of several milking parameters, and in that the deactivation threshold is determined at least partially with the aid of the values of at least two measured milking parameters.
 19. A method as claimed in any one of the preceding claims, characterized in that the method comprises the step of determining, during obtaining a milk flow, the value of at least one milking parameter, and in that the deactivation threshold is determined at least partially with the aid of the value of the at least one measured milking parameter and a predetermined milking parameter value which is in particular based on historical data.
 20. A method as claimed in claim 19, characterized in that the method comprises the step of determining the difference between the momentary value of the milking parameter and the predetermined milking parameter value which is in particular based on historical data.
 21. A method as claimed in claim 18, characterized in that during step a) the value of the momentary milk flow, the value of the average of the milk flow and the value of the momentary electric conductivity of the obtained milk are determined.
 22. A method as claimed in claims 19 and 20, characterized in that the method comprises the step of storing the average, historical electric conductivity of the milk produced by the teat based on historical data.
 23. A method as claimed in claim 22, characterized in that the method comprises the step of determining the difference between the momentary electric conductivity and the average, historical electric conductivity.
 24. A method as claimed in claim 21, 22 or 23, characterized in that the method comprises the step of connecting at least one further teat cup to a further teat of the dairy animal, and the step of determining the electric conductivity of the milk obtained from said further teat.
 25. A method as claimed in claim 24, characterized in that the method comprises the step of determining the teat producing, in comparison with the other teats, at one point of time milk with the lowest electric conductivity, and in that for every other teat the deviation from the conductivity of the milk produced by that other teat, relative to the lowest conductivity of the milk obtained from the teat producing milk with the lowest conductivity, is determined.
 26. A method as claimed in claim 23 or 25, characterized in that the step of deactivating the teat cup is carried out at a point of time depending on the average milk flow and the difference in electric conductivity.
 27. A method as claimed in claim 26, characterized in that the method comprises the step of applying a mathematical function to the value of the average milk flow and the difference in electric conductivity for obtaining a compensated threshold milk flow average.
 28. A method as claimed in claim 27, characterized in that the function consists in multiplying the average milk flow by 10 and dividing it by the difference in electric conductivity.
 29. A method as claimed in any one of the preceding claims, characterized in that the step of deactivating the teat cup is carried out when the momentary value of the milking parameter during a period of time equals or is lower than the threshold milking parameter value.
 30. A method as claimed in claim 29, characterized in that the period of time is adjustable.
 31. A method as claimed in claim 30, characterized in that the period of time is adjustable between approximately 2 seconds and approximately 9 seconds.
 32. A method as claimed in any one of the preceding claims, said method comprising the step of disconnecting the teat cup, characterized in that the step of disconnecting the teat cup is carried out after a certain period of time after deactivation of the teat cup has elapsed.
 33. A method as claimed in claim 32, characterized in that the period of time is adjustable.
 34. A method as claimed in claim 33, characterized in that the period of time is adjustable between approximately 2 seconds and approximately 15 seconds.
 35. A method as claimed in any one of the preceding claims, characterized in that the automatic milking is carried out by a milking robot.
 36. A method as claimed in claim 35, characterized in that the admission criterion for the milking robot is at least adapted with the aid of the value of the milking parameter during step a).
 37. A device for automatically milking a dairy animal, in particular a cow, said device being provided with means for activating the teat cup for milking the teat of the dairy animal, means comprising a milking parameter for measuring a milking parameter during milking the teat for obtaining a milking parameter value, means for deactivating the teat cup, and means for generating a threshold signal indicating that a deactivation threshold has been reached, the deactivation means being put into operation with the aid of the threshold signal, characterized in that the means for generating the signal indicating a deactivation threshold generate at least partially the signal with the aid of the milking parameter value.
 38. A device as claimed in claim 37, characterized in that the device is provided with a computer, in that the milking parameter is capable of being connected with the computer for transmitting milking parameter data to the computer, in that the computer is suitable for storing the starting time from which the milking parameter is measured, is suitable for storing the momentary value of the milking parameter as measured by the milking parameter meter, and is suitable for continuously determining the average value of the milking parameter, the means for deactivating the teat cup being controlled with the aid of data based on the average value of the milking parameter determined by the computer.
 39. A device as claimed in claim 38, characterized in that the computer is suitable for applying a mathematical function to the value of the average value of the milking parameter for obtaining a threshold milking parameter average.
 40. A device as claimed in claim 39, characterized in that the computer comprises a comparator for comparing the momentary value of the milking parameter with the threshold milking parameter average.
 41. A device as claimed in any one of the preceding claims 38 through 40, characterized in that the computer is provided with a memory for storing a number of ranges of average values of the milking parameter, and for storing a respective milking parameter threshold value corresponding with a certain range.
 42. A device as claimed in claim 41, characterized in that the computer comprises a comparator for comparing the average value of the milking parameter with the ranges stored in the memory.
 43. A device as claimed in claim 39, characterized in that the function consists in dividing by
 3. 44. A device as claimed in claim 39, characterized in that the function consists in dividing by S.
 45. A device as claimed in any one of the preceding claims 38 through 44, characterized in that the device is provided with several milking parameter meters for determining the values of several milking parameters, the means for deactivating the teat cup being controlled with the aid of data based on the average values of the milking parameters determined by the computer.
 46. A device as claimed in claim 45, characterized in that the device is provided with a milk flow meter for measuring the momentary milk flow and a conductivity meter for determining the momentary electric conductivity of the obtained milk.
 47. A device as claimed in claim 46, characterized in that the computer is suitable for storing the average, historical electric conductivity of the teat based on historical data.
 48. A device as claimed in claim 47, characterized in that the computer is suitable for determining the difference between the momentary electric conductivity and the average, historical electric conductivity.
 49. A device as claimed in claim 46, 47 or 48, characterized in that the device comprises at least one further teat cup capable of being connected to a further teat of the dairy animal, and an electric conductivity meter for determining the electric conductivity of the milk obtained from said further teat.
 50. A device as claimed in claim 49, characterized in that the computer is suitable for determining the teat which in comparison with the other teats produces at one point of time milk with the lowest electric conductivity, and for determining for every other teat the deviation from the conductivity of the milk produced by said other teat relative to the lowest conductivity of the milk obtained from the teat producing the milk with the lowest conductivity.
 51. A device as claimed in claim 48 or 50, characterized in that the means for deactivating the teat cup are put into operation by the computer at a point of time depending on the average milk flow and the difference in electric conductivity.
 52. A device as claimed in claim 51, characterized in that the computer is suitable for applying a mathematical function to the value of the average milk flow and the difference in electric conductivity for obtaining a compensated threshold milk flow average.
 53. A device as claimed in claim 52, characterized in that the function consists in multiplying the average milk flow by 10 and dividing it by the difference in electric conductivity.
 54. A device as claimed in any one of the preceding claims 37 through 53, characterized in that the device is constituted by a milking robot comprising means for automatically connecting respectively disconnecting the teat cup(s).
 55. A device as claimed in claim 54, characterized in that the computer is suitable for determining a period of time from deactivation of the teat cup and for putting the means for disconnecting the teat cup(s) into operation when the period of time has reached a certain time threshold value.
 56. A device as claimed in claim 55, characterized in that the time threshold value is adjustable.
 57. A device as claimed in claim 56, characterized in that the time threshold value is adjustable between approximately 2 seconds and approximately 15 seconds. 